Megalocornea

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Background

Megalocornea is a rare nonprogressive enlargement of the cornea to 13 mm or greater; in the setting of normal intraocular pressure. The cornea and limbus are enlarged, but the cornea itself is histologically normal and of normal thickness. Megalocornea is usually seen as an isolated finding, known as simple isolated megalocornea. It may be associated with other ocular and systemic findings, including megophthalmos anterior and/ or dysgenesis of the iris, lens, and ciliary body.

Megalocornea is shown in the image below.



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Megalocornea.

Pathophysiology

Megalocornea is a developmental anomaly of unknown etiology. Postulated mechanisms of development include a defect in formation of the optic cup in which the anterior tips of the cup fail to fuse, allowing more space for the developing cornea. This is considered a primary overgrowth of the cornea, producing a normal endothelial cell density. In congenital glaucoma, the main differential diagnosis, the cell density is low due to distention of the cornea from elevated intraocular pressure. The cornea does not reach its full adult size until age 12 months; thus, a definitive diagnosis of megalocornea cannot be ruled out until after this time.

Epidemiology

Frequency

United States

No data are available.

International

No data are available.

Mortality/Morbidity

Morbidity and mortality can be secondary to the many systemic conditions found in association with megalocornea. See Special Concerns.

Ocular morbidity is associated with anterior megalophthalmos. An enlarged ciliary ring causes zonular stretching, leading to phacodonesis, ectopia lentis, iridodonesis, iris stromal hypoplasia and transillumination defects, Krukenberg spindles, and trabecular meshwork pigmentation. Other findings are posterior embryotoxon, Rieger anomaly, goniodysgenesis, and cataracts. Goniodysgenesis and pigment dispersion can contribute to glaucoma.

Sex

Males account for 90% of cases because X-linked recessive inheritance is most common.

Age

Megalocornea is present from birth.

History

Megalocornea is present from birth.

A family history of megalocornea may be present.

The mother may have slightly enlarged corneas.

Physical

Findings of simple megalocornea

See the list below:

Findings of anterior megalophthalmos

See the list below:

Findings of congenital glaucoma not found in megalocornea

See the list below:

Causes

Megalocornea is inherited as an X-linked recessive trait (90% of cases).

The gene locus for X-linked megalocornea is in band Xq12-q26, most likely band Xq21-q23.

Autosomal dominant, autosomal recessive, and sporadic inheritance have been reported.

Other Tests

Gonioscopy

Widened ciliary ring indicates anterior megalophthalmos.

Check for excessive mesenchymal tissue in the angle.

A-scan ultrasound biometry

Buphthalmos may indicate congenital glaucoma.

Findings with megalocornea but not congenital glaucoma - Increased anterior chamber depth, posterior lens-iris diaphragm position, and short vitreous length

Specular microscopy

Normal endothelial cell density in megalocornea

Decreased endothelial cell density in congenital glaucoma

Histologic Findings

The cornea is histologically normal.

Medical Care

Medical care for patients with megalocornea includes correction of refractive error and thorough evaluation for findings of anterior megalophthalmos. Also, routine examination for the development of cataracts and glaucoma is necessary.

Surgical Care

Surgical amelioration of glaucoma and cataract is performed when necessary.

Cataract is common with megalocornea, and the cataract surgery is difficult. The zonules supporting the lens capsule surrounding the cataract are often weak. Weakened zonules make it more difficult to support an artificial intraocular lens (IOL). This leads to increased surgical complications, such as vitreous loss and loss of lens material to the back of the eye during cataract surgery.[1, 2, 3]

The large size of the anterior segment makes IOL selection difficult as standard IOLs are too small. A standard lens will often not work. Oetting and Newsom at the University of Iowa reported on the use of a special IOL called the Artisan lens (see the image below) that clips onto the iris.[4]



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Megalocornea patient with Artisan lens.

Because this IOL clips onto the iris rather than fitting into the angle, it allows for a safe and stable placement, even with the large anterior segment. Basti and colleagues reported using suture based iris fixation to allow placement of a standard IOL in these large eyes.[5]

Consultations

Pediatric developmental specialist consultation is always indicated to evaluate for the many associated systemic conditions. These include albinism, Down syndrome, Marfan syndrome, Alport syndrome, craniosynostosis, and many others.

Further Outpatient Care

Patients with megalocornea should have regular examinations to detect glaucoma or cataract.

Complications

Complications of megalocornea may include the following:

Prognosis

The prognosis is excellent in simple megalocornea. Patients with anterior megalophthalmos will always be at risk for glaucoma and cataracts, which can be difficult to treat in these patients.

Patient Education

Advise parents of the potential for ocular complications and associated systemic conditions. Emphasize the importance of a thorough developmental evaluation and regular medical and ophthalmic follow-up care.

Author

Mark Ventocilla, OD, FAAO, Adjunct Clinical Professor, Michigan College of Optometry; Editor, American Optometric Association Ocular Surface Society Newsletter; Chief Executive Officer, Elder Eye Care Group, PLC; Chief Executive Officer, Mark Ventocilla, OD, Inc; President, California Eye Wear, Oakwood Optical

Disclosure: Nothing to disclose.

Coauthor(s)

Lee S Webster, MD, Ophthalmologist, Shoreline Vision

Disclosure: Nothing to disclose.

Specialty Editors

Simon K Law, MD, PharmD, Clinical Professor of Health Sciences, Department of Ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles, David Geffen School of Medicine

Disclosure: Nothing to disclose.

Christopher J Rapuano, MD, Professor, Department of Ophthalmology, Sidney Kimmel Medical College of Thomas Jefferson University; Director of the Cornea Service, Co-Director of Refractive Surgery Department, Wills Eye Hospital

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Cornea Society, AAO, OMIC, Avedro; Bio-Tissue; GSK, Kala, Novartis; Shire; Sun Ophthalmics; TearLab<br/>Serve(d) as a speaker or a member of a speakers bureau for: Avedro; Bio-Tissue; Shire<br/>Received income in an amount equal to or greater than $250 from: AAO, OMIC, Avedro; Bio-Tissue; GSK, Kala, Novartis; Shire; Sun Ophthalmics; TearLab.

Chief Editor

Hampton Roy, Sr, MD, Associate Clinical Professor, Department of Ophthalmology, University of Arkansas for Medical Sciences

Disclosure: Nothing to disclose.

Additional Contributors

Fernando H Murillo-Lopez, MD, Senior Surgeon, Unidad Privada de Oftalmologia CEMES

Disclosure: Nothing to disclose.

Acknowledgements

Mark A Hendrix, MD Consulting Staff, Department of Ophthalmology, Suburban Hospital, Shady Grove Hospital

Mark A Hendrix, MD is a member of the following medical societies: American Academy of Ophthalmology and American Medical Association

Disclosure: Nothing to disclose.

Thomas A Oetting, MD Professor, Residency Program Director, Department of Ophthalmology, University of Iowa Carver College of Medicine

Thomas A Oetting, MD is a member of the following medical societies: American Academy of Ophthalmology and American Society of Cataract and Refractive Surgery

Disclosure: Nothing to disclose.

References

  1. Saatci AO, Soylev M, Kavukcu S, Durak I, Saatci I, Memisoglu B. Bilateral megalocornea with unilateral lens subluxation. Ophthalmic Genet. 1997 Mar. 18(1):35-8. [View Abstract]
  2. Wang QW, Xu W, Zhu YN, Li JY, Zhang L, Yao K. Misdiagnosis induced intraocular lens dislocation in anterior megalophthalmos. Chin Med J (Engl). 2012 Sep. 125(17):3180-2. [View Abstract]
  3. Khan AO, Aldahmesh MA, Alkuraya FS. Congenital megalocornea with zonular weakness and childhood lens-related secondary glaucoma - a distinct phenotype caused by recessive LTBP2 mutations. Mol Vis. 2011. 17:2570-9. [View Abstract]
  4. Oetting TA, Newsom TH. Bilateral Artisan lens for aphakia and megalocornea: Long-term follow-up. J Cataract Refract Surg. 2006 Mar. 32(3):526-8. [View Abstract]
  5. Basti S, Koch DD. Secondary peripheral iris suture fixation of an acrylic IOL in megalocornea. J Cataract Refract Surg. 2005 Jan. 31(1):7; author reply 8. [View Abstract]
  6. Assia EI, Segev F, Michaeli A. Cataract surgery in megalocornea Comparison of 2 surgical approaches in a single patient. J Cataract Refract Surg. 2009 Dec. 35(12):2042-6. [View Abstract]
  7. Chang DF. Siepser slipknot for McCannel iris-suture fixation of subluxated intraocular lenses. J Cataract Refract Surg. 2004 Jun. 30(6):1170-6. [View Abstract]
  8. Kraft SP, Judisch GF, Grayson DM. Megalocornea: a clinical and echographic study of an autosomal dominant pedigree. J Pediatr Ophthalmol Strabismus. 1984 Sep-Oct. 21(5):190-3. [View Abstract]
  9. Mackey DA, Buttery RG, Wise GM, Denton MJ. Description of X-linked megalocornea with identification of the gene locus. Arch Ophthalmol. 1991 Jun. 109(6):829-33. [View Abstract]
  10. Maumenee IH. The cornea in connective tissue diseases. Ophthalmology. 1978 Oct. 85(10):1014-7. [View Abstract]
  11. Meire FM. Megalocornea. Clinical and genetic aspects. Doc Ophthalmol. 1994. 87(1):1-121. [View Abstract]
  12. Meire FM, Bleeker-Wagemakers EM, Oehler M, Gal A, Delleman JW. X-linked megalocornea. Ocular findings and linkage analysis. Ophthalmic Paediatr Genet. 1991 Sep. 12(3):153-7. [View Abstract]
  13. Meire FM, Delleman JW. Biometry in X linked megalocornea: pathognomonic findings. Br J Ophthalmol. 1994 Oct. 78(10):781-5. [View Abstract]
  14. OMIM. Online Mendelian Inheritance in Man, OMIM(TM). McKusick-Nathans Institute for Genetic Medicine, Johns Hopkins University (Baltimore, MD) and National Center for Biotechnology Information, National Library of Medicine (Bethesda, MD), 2000. Available at: http://www.ncbi.nlm.gov/Omim/.
  15. Skuta GL, Sugar J, Ericson ES. Corneal endothelial cell measurements in megalocornea. Arch Ophthalmol. 1983 Jan. 101(1):51-3. [View Abstract]
  16. Srivastava AK, McMillan S, Jermak C, Shomaker M, Copeland-Yates SA, et al. Integrated STS/YAC physical, genetic, and transcript map of human Xq21.3 to q23/q24 (DXS1203-DXS1059). Genomics. 1999 Jun 1. 58(2):188-201. [View Abstract]
  17. Starck T, Hersh PS, Kenyon KR. Corneal dysgeneses, dystrophies, and degenerations. Principles and Practice of Ophthalmology. 2000. Vol 2: 695-696.
  18. Wood WJ, Green WR, Marr WG. Megalocornea: A clinico-pathologic clinical case report. Md State Med J. 1974 Jul. 23(7):57-60. [View Abstract]

Megalocornea.

Central mosaic dystrophy sometimes noted in megalocornea.

Megalocornea patient with Artisan lens.

Central mosaic dystrophy sometimes noted in megalocornea.

Megalocornea.

Megalocornea patient with Artisan lens.

B-scan ultrasound showing a large flat iris.

Aphakic megalocornea patient with 15 mm white to white.